Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$194.71	13.866%	$221.7085	$221.71	$221.70	$221.70
Purchase #2	$76.89	8.677%	$83.5617	$83.56	$83.55	$83.60
Purchase #3	$72.67	6.143%	$77.1341	$77.13	$77.15	$77.10
Purchase #4	$70.91	10.562%	$78.3995	$78.40	$78.40	$78.40
Purchase #5	$64.83	4.535%	$67.77	$67.77	$67.75	$67.80
Purchase #6	$196.86	10.221%	$216.9811	$216.98	$217.00	$217.00
Purchase #7	$223.91	4.132%	$233.162	$233.16	$233.15	$233.20
7 purchase totals =	$900.78		$978.7169	$978.71	$978.70	$978.80